1. Field of the Invention
The invention relates to a device for welding tubular components of plastics material, as characterized in the preamble of claim 1.
A device for welding tubular components is known in which the heatable jaws have at the inner circumference an annular duct in which a vacuum is generated during or after the welding process of the axially abutting tubular components. The vacuum has the purpose to prevent the molten material to drop inwardly or to prevent the formation of an inner bead at the welded connection. However, it has been found that it is not possible to manufacture welded connections by means of this method and by means of this device which are of sufficient strength and smooth at the inner circumference.
It is also known (DE-PS 283 0722), for reducing inner welding beads at the circumference of the tubular components, to arrange an elastic insert which presses against the inner welding bead.
However, for welding the tubular components, the ends thereof are heated by pressing them against heating elements and the ends are subsequently pressed together. A welded connection which is completely free of beads cannot be achieved by means of this method. In addition, by heating the front ends of the tubular components, the interior of these components may be contaminated, so that the necessary cleanliness is not achieved and the connection is not suitable for pipeline systems which conduct media having a high degree of purity.
A device of the above-mentioned type is known from DE-C2 29 23 205 by means of which welding of the ends of tubular plastic components which is free of beads is possible.
This device can only be used for one pipe dimension. The heating device has half shells of metal the middle portion of which is electrically heatable for the butt joint and the other portion at both ends seen in longitudinal direction is equipped with cooling chambers. This requires a complicated construction and a control of the individual zones which is very disadvantageous. In addition, the heating zone cannot be quickly cooled after the heating process which results in long welding times.